linux-kernel - Re: [PATCH] MMC: Add 400ms to CAFE SD controller resume path

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Date:	Sat, 13 Jun 2009 12:34:52 +0200
From:	Pierre Ossman <pierre@...man.eu>
To:	dsaxena@...xity.net
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MMC: Add 400ms to CAFE SD controller resume path

On Thu, 4 Jun 2009 23:33:49 +0000
Deepak Saxena <dsaxena@...xity.net> wrote:

> 
> The request is not ending up in the queue of the new device.  If I 
> recall correctyl What is happening is that userspace does an unmount on the 
> old device when it receives the notification that it is gone (since it is not 
> redected and a new entry is created). By the time that unmount is called, the 
> various data structures for the device has been zeroed out but the various 
> operation pointers are !NULL, so when we go back to write the superblock for 
> the mounted partition, we overwrite the device's partition table as the
> partition offset is now 0. The main issue here is that the kernel is allowing 
> an I/O to a device that is technically still there but not from the kernel's
> POV.

But if the device is not there from the kernel's POV then it should be
impossible to write to it. It seems this is a kernel bug though. See
this thread:

http://marc.info/?t=124413860500006&r=1&w=2

Rgds
-- 
     -- Pierre Ossman

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